Date of Award

Summer 2021

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)


Ocean Science and Engineering

Committee Chair

Dr. Robert J. Griffitt

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Dr. Leila Hamdan

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Dr. Maria Rodgers


The presence of oil has been shown to affect the microbiomes of the water column, sediments, and organisms, both by altering the diversity and the composition of those microbial communities. If the microbiome is altered it may no longer provide benefits to its host organism, impacting its ability to survive. Thus, it is important to understand the effects of large-scale contamination events including the Deepwater Horizon oil spill. This study set out to examine the effects of oil exposure on the microbiome of two benthic species, southern flounder (Paralichthys lethostigma) and eastern oysters (Crassostrea virginica) to further understand the effects of both short- and long-term oil contamination. The bacterial component of the microbiomes of the two species were analyzed using Next-Generation 16S Sequencing, focusing on diversity and taxonomic analysis of the bacteria present within the samples. Flounder were exposed to oiled sediments as well as a pathogenic bacteria (Vibrio anguillarum) challenge in a 17-day fully factorial laboratory experiment. Oysters were collected from reefs across the Mississippi Sound and the concentration of polycyclic aromatic hydrocarbons (PAHs) within the oyster tissue, shell and nearby sediment were measured. Analysis of the flounder microbiome showed significant responses to both the oil and pathogen exposure, but those responses differ between gill and intestine microbiomes. The oyster digestive gland microbiome showed no effect of the measured concentrations of PAHs in either shell, tissue, or nearby sediment. Reef location also showed no effect on the diversity or composition of the oyster microbiome.